Method and relative system for the measurement of the isotope ratio in hydrocarbons

ABSTRACT

Method for measurement of carbon isotope ratio in hydrocarbons obtainable from solid rock samples extracted from subsoil, preferably while oil drilling comprising pre-treatment of rock extracted from subsoil; scrubbing with inert gas of a rock sample taken from said rock; desorption, by heating, of a first gaseous sample containing hydrocarbons contained in pores of said rock sample and pyrolysis of said rock sample, said pyrolysis being suitable for obtaining a second gaseous sample from transformation of organic material of said rock sample; homogenisation and sampling of said first gaseous sample and, subsequently, said second gaseous sample; oxidation of said first gaseous sample and said second gaseous sample, said oxidation being suitable for obtaining carbon dioxide from hydrocarbons contained in said first gaseous sample and said second gaseous sample; separation of said carbon dioxide from other products of oxidation reaction and measurement of carbon isotope ratio in said carbon dioxide.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims the benefit of the priority filing date of Italian Patent Application No. MI2014A002166 filed on Dec. 17, 2014 in the name of GEOLOG S.r.I., the assignee. The earliest priority date claimed is Dec. 17, 2014.

FEDERALLY SPONSORED RESEARCH

Not Applicable

SEQUENCE LISTING OR PROGRAM

Not Applicable

BACKGROUND

The present invention relates to a method and relative system for the measurement of the isotope ratio in hydrocarbons obtainable from heating of solid rock samples extracted during the activity of oil drilling.

The state of art whereto the present invention relates is that of explorations of the subsoil performed in order to exploit the geothermal and oil resources thereof.

Exploration of the subsoil for the abovementioned purposes takes place by means of well drilling and the subsequent geochemical analysis of the following groups of elements:

-   -   volatile elements found in drilling muds brought to the surface     -   volatile elements found in solid drilling cuttings.

Elements of the second group, i.e. those found in the solid drilling cuttings, can be either already present in the pores of said samples or can be obtained following transformation of the organic material of said samples.

The quantitative analysis of the hydrocarbons present in the subsoil during drilling is, moreover, aimed at achieving the following two objectives:

determination of the concentration of the various hydrocarbons present;

measurement of the carbon isotope ratio in said hydrocarbons. In this respect it is customary to calculate, preferably, the ratio between the quantity of ¹³C and the quantity of ¹²C.

With the current state of the art, as regards the first group of elements (i.e. elements dissolved in the drilling mud), the first type of analysis (i.e. that relating to the determination of the concentration of the different hydrocarbon species), can be performed either in the laboratory, by means of the combined use of gas chromatography and mass spectrometry, or on site, combining the gas chromatography with sensors of thermal conductivity or flame ionisation detectors.

The second type of analysis (i.e. measurement of the carbon isotope ratio, relating to the first group of elements, said first group being constituted by elements dissolved in the drilling mud), can be performed either in the laboratory by means of a mass spectrometers of the IRMS (isotope ratio mass spectrometry) type or, on site, by means of a laser optical spectrometer combined with chromatography column and flame ionisation detectors. This latter type of system is, in particular, described in US patent application US20130064715 (Italian priority MI2011A001647) which relates to a system for the determination of the carbon isotope ratio in the hydrocarbons dissolved in the drilling mud, comprising: a chromatography column which separates the single gas species, a flame ionisation detector for the detection of said gas species; an oxidation device which transforms said gas species into a single predetermined gas species and, finally, a laser optical spectrometer, said spectrometer being specifically calibrated to measure the carbon isotope ratio in said predetermined gas species.

As regards instead the analysis of the second group of elements, said second group being constituted by the volatile elements present in the solid rocky cuttings, determination of the concentration of the different hydrocarbon species is performed, at the current state of the art, either in the laboratory, using mass spectrometry techniques, or on site, by means of systems such as, for example, that described in the US patent application US2014150527 (Italian priority MI2012A002080), which provides for the combination of a device for heating of the sample of solid rock with a chromatography column and a flame ionisation detector. A system of this type allows for determination of the concentration of the single hydrocarbon species already present in the pores of the solid sample, together with the total concentration of all the hydrocarbons which can be obtained by means of transformation of the solid organic material of the sample.

This system, although measuring the concentration of the hydrocarbons, is not able to perform the measurement of the carbon isotope ratio of said hydrocarbons.

In the current state of the art, in fact, there is no instrumentation able to perform, directly on site (i.e. where the drilling is carried out), the measurement of the carbon isotope ratio in the second group of elements, said second group being constituted by the elements found in the solid drilling cuttings.

An analysis of this type can be performed, at the current state of the art, only in the laboratory. The instruments necessary for performing such an analysis cannot in fact be transported on site due to the excessive dimensions of the spectrometers of the IRMS type. It is clear that, if the measurement of the carbon isotope ratio is performed in the laboratory, said measurement cannot be used for real time monitoring of the drilling and cannot be used to take decisions concerning the operations of drilling underway.

SUMMARY

The object of the present invention is therefore that of providing a method and relative system which allows the performance in situ, i.e. on site, of the measurement of the carbon isotope ratio in hydrocarbons contained in a solid rock sample, extracted from the subsoil during oil drilling. The present invention therefore sets out to bridge the gap present in the state of the art by proposing a method and relative system able to perform on site the measurement of the carbon isotope ratio in the second group of elements mentioned above, said second group being constituted by elements found in the solid drilling cuttings. More particularly, the present invention allows for measurement of the carbon isotope ratio both in the hydrocarbons already present in the pores of said samples and in the hydrocarbons obtainable following transformation of the organic material of said samples.

The systems of the prior art, usable only in the laboratory, as well as not being transportable on site are, moreover, highly complex. For this reason, it is necessary to employ and train highly specialised staff both for their functioning and for their maintenance.

A second object of the present invention is therefore that of providing a method and relative system able to measure the carbon isotope ratio in hydrocarbons found in a solid rock sample extracted from the subsoil, preferably during oil drilling, which is simple to use also for not highly specialised technicians. In order to use the system of the present invention, it is sufficient in fact to train the staff already normally present at an oil drilling site, without having to use specific human resources for this system.

The systems and the methods currently used in the prior art, in addition to having limitations of use due to the non-transportability to the drilling site, and due to the need for use of highly qualified staff, have a further disadvantage linked to the long periods of time necessary in order to be able to carry out the measurements.

A further object of the present invention is therefore that of providing a method and relative system able to measure the carbon isotope ratio in hydrocarbons found in a solid rock sample extracted from the subsoil, preferably during oil drilling, which is characterised by reduced measurement times, i.e. substantially lower than those of the instruments of the prior art. The system of the present invention in fact provides an overall time below one hour for performing the total analysis, as will be made clearer by the detailed reading here below.

These and further objects are achieved by the present invention by means of a method and relative system which provides both for the extraction of gases present in the pores of rock taken from the subsoil and for obtaining gas through transformation of the organic material of said rock directly at the drilling site. This is carried out by means of a special oven, suitable for obtaining said gases through heating of said rock, said gases comprising both the gases present in the pores of said rock and the gases obtainable from the transformation of the organic material of said rock. The method and the relative system which form the object of the present invention, moreover, provide that the measurement of the carbon isotope ratio is not performed directly on the hydrocarbons obtained from the rock taken from the subsoil by means of heating in said oven, but that such measurement is, instead, performed on the carbon dioxide obtained from said hydrocarbons following oxidation of the same. Said measurement of the carbon isotope ratio in the carbon dioxide will correspond to the isotope ratio in the hydrocarbons from which said carbon dioxide was obtained, to the extent wherein the oxidation reaction takes place 100%. To this end, the method and relative system that form the object of the present invention provide that specific catalysts be used in the oxidation reaction mentioned above, capable of ensuring that said oxidation reaction is complete and that there are no losses of carbon in the transformation of the hydrocarbons into carbon dioxide.

These and further features of the present invention will be made clearer by reading of the following detailed description, relating to a preferred embodiment of the present invention to be considered by way of a non-limiting example of the more general concepts claimed.

DRAWINGS

The following description refers to the accompanying drawings, in which:

FIG. 1 is a diagram as an example of the method as a whole;

FIG. 2 is a simplified representation of the system that implements the method which is the object of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring to FIG. 1, the solid rock extracted from the borehole during drilling undergoes a series of operations of pre-treatment (1) which consist of:

-   -   first washing with water of the rock extracted;     -   first drying of said rock in an oven at a temperature of 60-70°         C.;     -   grinding of said rock with an electric mill;     -   scrubbing of said rock with hydrochloric acid or phosphoric acid         for the removal of the carbonate fraction present in said rock.         The removal of the carbonates present in the sample is necessary         in that, in a successive phase of the process referred to as         oxidation, the carbonates present in the extracted rock could         react with the oxygen giving rise to carbon dioxide, altering         the final measurement of the carbon isotope ratio, as will be         made clearer from the reading here below.     -   second washing with water. Said second washing with water is         intended to remove the hydrochloric acid or the phosphoric acid         used for the previous removal of the carbonates. This second         washing is necessary because the residues of hydrochloric or         phosphoric acid remaining during the previous step can give rise         to phenomena of corrosion in the instrumentation used for the         successive steps.     -   second drying of said rock in oven at a temperature of 60-70°         C.;     -   taking of a rock sample (C) for the successive steps of the         process.

At the end of the operations of pre-treatment (1) the rock sample (C), taken previously, is ready to be subjected to the operation of desorption (2) of the hydrocarbons already present in the pores of said rock sample (C). Before said phase of desorption (2), inside the instrument, an operation of scrubbing (2 a) of the sample (C) with an inert gas, for example nitrogen, is carried out. At the end of said scrubbing operation (2 a) the phase of desorption (2) is carried out which consists of heating, inside an oven in an inert atmosphere free from oxygen, of said rock sample (C) up to a first temperature value, said first value of temperature being equal to 300° C. Said first temperature value is maintained for approximately 5 minutes. The effect of the desorption (2) is that of extracting a first gaseous sample (S1) containing hydrocarbons, said hydrocarbons being of said first gaseous sample (S1), present in the pores of said rock sample (C).

After the phase of desorption (2), the method which is the object of the present invention provides a phase of homogenisation and of sampling (3) of said first gaseous sample (S1) previously desorbed from the rock sample (C), said phase of homogenisation and sampling (3) being aimed at sampling small quotas (A1) of the first gaseous sample (S1).

The single quotas (A1) taken from said first gaseous sample (S1) are then subjected to a phase of oxidation (4), wherein the gas mixture contained in said quotas (A1) is made to react with oxygen, at a temperature comprised between 500° C. and 900° C., giving rise to the formation of carbon dioxide CO₂ and water H₂O. Again during the phase of oxidation (4) also any other gas species are oxidated which are not hydrocarbons (such as for example sulphurates) but which can in any case have been desorbed from the rock sample (C) during the operation of heating and, therefore, can be present in the first gaseous sample (S1). In this case, the products of the oxidation will be water H₂O and the respective anhydrides (for example, in the case of sulphurates, sulphuric anhydride SO₂).

The phase of oxidation (4) is followed by a phase of separation (5) of the carbon dioxide CO₂ from the other products of the oxidation reaction, such as water and the other possible anhydrides.

The carbon dioxide CO₂ appropriately separated from the other species derived from the oxidation is subjected to the successive phase of measurement (6) of the carbon isotope ratio contained in said CO₂. Said carbon isotope ratio contained in the CO₂ will correspond to the carbon isotope ratio in the hydrocarbons previously desorbed (S1) to the extent wherein there is no loss of carbon during the reaction of oxidation. It is therefore necessary that the reaction of oxidation takes place 100% in order to avoid errors in the estimate of the carbon isotope ratio in the desorbed hydrocarbons contained in said first gaseous sample (S1).

After the desorption (2) of the hydrocarbons (S1) already present in the pores of the rock sample (C), said rock sample (C) is subjected to a further phase of heating, called phase of pyrolysis (2′). Before said phase of pyrolysis (2′) the rock sample (C), from which the hydrocarbons (S1) have previously been desorbed, is subjected again to the operation of scrubbing (2 a) with inert gas. Said operation of scrubbing (2 a), which has a duration varying between 30 and 60 seconds, has as a further object, that of cleaning the oven where the previous desorption (2) took place of possible traces of hydrocarbons (S1) previously desorbed. At the end of said scrubbing operation (2 a) the phase of pyrolysis (2′) is carried out which consists of a controlled heating up to a temperature of 650° C. Once this temperature has been reached it is maintained for approximately 5 minutes.

The effect of the pyrolysis (2′) is that of obtaining a second gaseous sample (S2) containing hydrocarbons derived from transformation of the organic material of the rock sample (C).

The second gaseous sample (S2), obtained following the phase of pyrolysis (2′), undergoes a process similar to that undergone by said first gaseous sample (S1). The phases of the process whereto said second gaseous sample (S2) are subjected are, in any case, given here below, for completeness.

After the phase of pyrolysis (2′) said second gaseous sample (S2) undergoes a phase of homogenisation and of sampling (3).

The hydrocarbons of said second gaseous sample (S2) are then subjected to a phase of oxidation (4), wherein said hydrocarbons are made to react with oxygen, at a temperature between 500° C. and 900° C., giving rise to the formation of carbon dioxide CO₂ and water H₂O.

The phase of oxidation (4) is followed by a phase of separation (5) of the carbon dioxide CO₂ from the other products of the oxidation reaction, such as water and other possible anhydrides which can be formed by oxidation of the other non-hydrocarbon gas species present in said second gaseous sample (S2).

The carbon dioxide CO₂ appropriately separated from the other species derived from the oxidation is subjected to the successive phase of measurement (6) of the carbon isotope ratio in CO₂. In this case too it is necessary that the reaction of oxidation takes place 100% in order to avoid errors in the estimate of the carbon isotope ratio in the hydrocarbons obtained from the transformation of the organic material of the rock sample (C), said hydrocarbons being contained in said second gaseous sample (S2).

The phase of pyrolysis (2′), together with the scrubbing of the rock sample (C) and of the oven after desorption (2), can also take place simultaneously to the phases of homogenisation and sampling (3) of the first gaseous sample (S1); with the sole expedient that the phase of homogenisation and sampling (3) of the second gaseous sample (S2) takes place only after the phase of homogenisation and sampling (3) of the first gaseous sample (S1) has ended. This aspect will be made clearer from the detailed reading of the following description relating to the system which allows the process described hitherto to be implemented.

The phase of pyrolysis (2′) having ended and after the second gaseous sample (S2) has been sent to the successive phase of homogenisation and sampling (3), the oven used for the phase of desorption (2) first and for the phase of pyrolysis (2′) later is then cooled to 300° C. and simultaneously scrubbed with inert gas so as to be prepared for a subsequent analysis.

Referring to FIGS. 1 and 2, the system which allows implementation of the method proposed by the present invention provides for the presence of an oven (7) suitable for performing the heating of the rock sample (C) for the purpose of desorption (2) and of pyrolysis (2′).

After the operations of pre-treatment (1), described previously, the rock sample (C) taken from the solid rock extracted from the borehole during drilling is inserted in a specific container (8), commonly referred to in the art with the term “vial”. This container (8) is then inserted on a cap (9), said cap (9) being suitable for closing an oven (7), said oven (7) being suitable for performing the desorption (2) subsequently.

The container (8) is then inserted in the oven (7) so that said cap (9) closes said oven (7). Scrubbing (2 a) of the rock sample (C) is then performed with inert gas, preferably nitrogen. The flow of nitrogen and the pressure inside said oven (7) are regulated, respectively, by a first solenoid valve (10) and a second solenoid valve (11). During the scrubbing with nitrogen, said first solenoid valve (10) and said second solenoid valve (11) are open. At the end of the scrubbing with nitrogen said first solenoid valve (10) is closed and said oven (7) with inside the container (8) containing the rock sample (C) is brought to atmospheric pressure. Closure of said second solenoid valve (11) subsequently takes place. The rock sample (C) is then heated up to a temperature of 300° C. and maintained at this temperature for approximately 5 minutes. Thanks to this heating, desorption (2) takes place of the first gaseous sample (S1) containing the hydrocarbons present in the pores of the rock sample (C).

By means of the opening of said first solenoid valve (10) said oven (7) is pressurised so that the first gaseous sample (S1) extracted through desorption (2) is transferred into a sampling cell (12). Said sampling cell (12) is brought to atmospheric pressure by means of a third solenoid valve (13).

The constant and repeatable sampling of a small quota (A1) of said first gaseous sample (S1) is guaranteed by a sampling valve (14). Said sampling valve (14) is a six-way rotary valve (14 a, 14 b, 14 c, 14 d, 14 e, 14 f) and the connection between the third way (14 c) and the sixth way (14 f) of the sampling valve constitutes the sampling cell (12).

The sampling valve (14) is switchable between two operative conditions corresponding to two separate phases of the process. In the first state of switching the ways (14 a) and (14 f), (14 d) and (14 e), (14 b) and (14 c) are in paired communication, while in the second operative condition the ways (14 e) and (14 f), (14 c) and (14 d), (14 a) and (14 b) are in paired communication.

When the sampling valve (14) is in said first state of switching, said first gaseous sample (S1) is transferred from said oven (7), where desorption (2) took place, to said sampling cell (12).

Once this transfer has taken place said sampling valve (14) passes to the second state of switching and a quota (A1) of said first gaseous sample (S1) passes from the sampling cell (12) to the oxidator (15) transported by a carrier gas, for example nitrogen, sent to the sampling valve (14) by means of opening of a valve (19). Simultaneously the first solenoid valve (10) and the second solenoid valve (11) open and the oven (7) is scrubbed with inert gas, for example nitrogen, to eliminate possible traces of the first gaseous sample (S1) remaining in said oven (7). Once a time varying between 30 and 60 seconds has passed, said first solenoid valve (10) closes, interrupting the flow of inert gas, and said oven (7) is brought to atmospheric pressure. Closure of said second solenoid valve (11) subsequently takes place. The oven (7) is then brought to a temperature of 650° C. This temperature is maintained for approximately 5 minutes and, in this way, pyrolysis (5) takes place, i.e. the transformation of the organic material of the rock sample (C). A second gaseous sample (S2) is thus produced, containing the hydrocarbons obtained from this transformation. At this point of the process, the sampling valve (14) returns into the first state of switching. Said second gaseous sample (S2) is then transferred into the sampling cell (12) and in the oxidator (15) oxygen is sent by means of opening of a fourth solenoid valve (18).

The quota (A1) of the first gaseous sample (S1) which is in the oxidator (15) undergoes transformation of oxidation at a temperature comprised between 500° C. and 900° C., giving rise to the formation of carbon dioxide CO₂ and water H₂O as well as other products derived from the oxidation of non-hydrocarbon substances. So that the oxidation reaction is 100%, the oxidator (15) contains in its interior a specific catalyst that can be, for example, copper chromite, copper oxide, or hopcalite.

The products of the reaction of oxidation of the gases contained in the quota (A1) taken from the first gaseous sample (S1) are sent to a chromatography column (16) that separates the carbon dioxide CO₂ from the other species.

The carbon dioxide CO₂ in output from said chromatography column (16) is then sent to a laser isotope analyser (17) which determines the carbon isotope ratio in the CO₂. Said carbon isotope ratio in the CO₂ will correspond to the isotope ratio of the hydrocarbons contained in said first gaseous sample (S1), first gaseous sample (S1) being obtained from the desorption (2) of gases contained in the pores of said rock sample (C).

At this point the sampling valve (14) passes to the second state of switching and a quota (A2) of said second gaseous sample (S2) is transferred from the sampling cell (12) to the oxidator (15). The sampling valve (14) returns to the first state of switching and the quota (A2) of the second gaseous sample (S2) which is in the oxidator (15) undergoes, as in the case of the quota (A1) taken from the first gaseous sample (S1), the transformation of oxidation (4) at a temperature between 500° C. and 900° C., giving rise to the formation of carbon dioxide CO₂ and water H₂O, as well as other products derived from the oxidation of non-hydrocarbon substances. The products of the reaction of oxidation are then sent to a chromatography column (16) that separates the carbon dioxide CO₂ from the other species. The carbon dioxide CO₂ in output from said chromatography column (16) is then sent to a laser isotope analyser (17) for the measurement of the carbon isotope ratio in the CO₂.

The oven (7) where the desorption (2) and the pyrolysis (2′) have taken place is then cooled to 300° C., the cap (9) is opened and the container (8) containing the analysed rock sample (C), is removed, so as to prepare the system for the successive analysis.

The invention described above achieves the objects set, overcoming the disadvantages of the prior art.

Thanks to the idea of measuring the carbon isotope ratio not directly in the hydrocarbons extracted from the solid rock, but indirectly measuring the isotope ratio in the carbon dioxide obtained from the oxidation of said hydrocarbons, it is possible to use instrumentation which is relatively simple to use and reduced in size so as to be transportable on site. The use, moreover, of a single oven, suitable for obtaining, by heating, both gases present in the pores of said rock and the gases obtainable from transformation of the organic material of said rock, together with use of a laser isotope analyser, allows for the development of a system characterised by operating times substantially lower than those of the instruments of the prior art. 

What is claimed is:
 1. A method for measurement of a carbon isotope ratio in hydrocarbons obtainable from solid rock samples extracted from subsoil, preferably while oil drilling, wherein said method comprises the following steps: pre-treatment of rock extracted from the subsoil; scrubbing with inert gas of a rock sample (C) taken from the rock previously subjected to said pre-treatment operation; desorption of a first gaseous sample (S1) containing hydrocarbons contained in pores of said rock samples (C), said desorption being performed by means of heating of said rock sample (C); homogenisation and sampling of said gaseous sample (S1), said sampling being suitable for obtaining quotas (A1) of said first gaseous sample (S1); oxidation of each of said gaseous quotas (A1) taken from said first gaseous sample (S1), said oxidation (4) being suitable for obtaining carbon dioxide CO₂ from the hydrocarbons contained in said first gaseous sample (S1); separation of said carbon dioxide CO₂ from other products of the reaction of oxidation, said carbon dioxide CO₂ being obtained from oxidation of each of said gaseous quotas (A1) taken from said first gaseous sample (S1); and measurement of the carbon isotope ratio in said carbon dioxide CO₂, said carbon dioxide CO₂ being obtained from oxidation of each of said gaseous quotas (A1) taken from said first gaseous sample (S1).
 2. The method according to claim 1, further comprising the steps of: scrubbing with inert gas of said rock sample (C) after said rock sample (C) has been subjected to said desorption; pyrolysis of said rock sample (C), said pyrolysis being suitable for obtaining a second gaseous sample (S2) from transformation of the organic material of said rock sample (C); homogenisation and sampling of said second gaseous sample (S2), said sampling being suitable for obtaining quotas (A2) of said second gaseous sample (S2); oxidation of each of said gaseous quotas (A2) taken from said second gaseous sample (S2), said oxidation being suitable for obtaining carbon dioxide CO₂ from the hydrocarbons contained in said second gaseous sample (S2); separation of said carbon dioxide CO₂ from other products of the reaction of oxidation, said carbon dioxide CO₂ being obtained from oxidation of each of said gaseous quotas (A2) taken from said second gaseous sample (S2); and measurement of the carbon isotope ratio in said carbon dioxide CO₂, said carbon dioxide CO₂ being obtained from the oxidation of each of said gaseous quotas (A2) taken from said second gaseous sample (S2).
 3. The method according to claim 1, wherein said step of pre-treatment of the rock extracted from the subsoil comprises the following operations: first washing with water of said rock extracted from the subsoil; first drying of said rock in oven at a temperature of 60-70° C.; grinding of said rock with known grinding means; scrubbing of said rock with acid, said scrubbing with acid suitable for removing the carbonate fraction present in said rock; second washing with water, said second washing with water being suitable for removing said acid; second drying of said rock at a temperature of 60-70° C.; and taking of a rock sample (C) from said rock.
 4. The Method according to claim 2, wherein said scrubbing with inert gas has a time duration comprised between 30 and 60 seconds.
 5. The Method according to claim 1, wherein said reaction of oxidation takes place 100%, said reaction of oxidation generating, among the reaction products, carbon dioxide CO₂, the isotope ratio of said carbon dioxide CO₂ being identical to the isotope ratio of the reacting hydrocarbons.
 6. The method according to claim 1, wherein said desorption is performed by means of a heating of said rock sample (C) up to a temperature of 300° C., said temperature being maintained for about 5 minutes.
 7. The method according to claim 2, wherein said pyrolysis is performed by means of a heating of said rock sample (C) up to a temperature of 650° C., said temperature being maintained for about 5 minutes.
 8. The Method according to claim 1, wherein said oxidation takes place at a temperature comprised between 500° C. and 900° C.
 9. The Method according to claim 1, wherein said inert gas is nitrogen N₂.
 10. The Method according to claim 1, wherein said inert gas is helium He.
 11. A System for measurement of carbon isotope ratio in hydrocarbons obtainable from solid rock samples extracted from subsoil, preferably while oil drilling, characterised in that said system comprises: an oven, said oven being suitable for heating a solid rock sample (C) so as to cause desorption of the gases (S1) present in pores of said rock sample (C), and said oven being suitable for heating a rock sample (C) so as to cause pyrolysis of said rock sample (C), said pyrolysis generating gases (S2) from transformation of organic material of said sample (C); a first solenoid valve suitable for regulating flow of an inert gas inside said oven; a second solenoid valve suitable for regulating pressure inside said oven; a sampling valve, said valve being suitable for sampling gases (S1, S2) coming from said oven, said gases being produced by desorption and by pyrolysis of said rock sample (C); an oxidator wherein gases (S1, S2) coming from said oven, said gases being produced by desorption and by pyrolysis of said rock sample (C), undergo a reaction of oxidation, said reaction of oxidation being suitable for producing carbon dioxide CO₂ when said gases (S1, S2) come from said oven, said gases being produced by desorption and by pyrolysis of said rock sample (C), are hydrocarbons; a chromatography column suitable for separating said carbon dioxide CO₂ from other products of said oxidation reaction; and a laser isotope analyser suitable for measuring carbon isotope ratio in said carbon dioxide CO₂ in output from said chromatography column.
 12. The System according to claim 11, wherein said sampling valve is a six-way rotary valve, said sampling valve being switchable between a first state of commutation and a second state of commutation.
 13. The System according to claim 12, wherein two ways of said sampling valve are connected in such a way as to form a sampling cell.
 14. The System according to claim 13, wherein said first state of commutation of said sampling valve is suitable for transferring gases (S1, S2) contained in said oven in said sampling cell, said gases being produced by desorption and by pyrolysis of said rock sample (C).
 15. The System according claim 14, wherein said second state of commutation of said sampling valve is suitable for transferring gases (S1, S2) contained in said sampling cell to said oxidator, said gases being produced by desorption and by pyrolysis of said rock sample (C).
 16. The System according to claim 15, comprising a third solenoid valve, suitable for regulating pressure in said sampling cell.
 17. The System according to claim 11, comprising a fourth solenoid valve, suitable for regulating flow of oxygen in said oxidator.
 18. The System according to claim 11, wherein said oxidator contains in its interior a catalyst such as for example: copper chromite, copper oxide or hopcalite. 